It's no secret that the world's population growth is heavily skewed by region — so much so that the changes expected for the next century will radically change the world as we know it.

But according to projections recently revised by the United Nations Population Program, those changes will come even faster than we thought.

The UN has dispensed with the old estimate that Africa's population will triple within 90 years — instead, it could very well quadruple.

Developed countries, especially in Europe, are more liable to shrink — an alarming prospect since low fertility rates mean that young, working citizens will be in short supply, and thereby less able to support aging societies.

The Nigerian story is an incredible one; its population, currently around 170 million, is already Africa's largest and is expected to be eight times greater within a scant 100 years. This presents a massive challenge for the central government, which is keen to promote family planning and already faces poverty rates of more than 60 percent and rising.